'\" te
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.TH DDI_FFS 9F "Jan 16, 2021"
.SH NAME
ddi_ffs, ddi_fls \- find first (last) bit set in a long integer
.SH SYNOPSIS
.nf
#include <sys/conf.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>



\fBint\fR \fBddi_ffs\fR(\fBlong\fR \fImask\fR);
.fi

.LP
.nf
\fBint\fR \fBddi_fls\fR(\fBlong\fR \fImask\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI).
.SH PARAMETERS
.ne 2
.na
\fB\fImask\fR\fR
.ad
.RS 8n
A 64-bit argument value to search through.
.RE

.SH DESCRIPTION
The function \fBddi_ffs()\fR takes its argument and returns the shift count
that the first (least significant) bit set in the argument corresponds to. The
function \fBddi_fls()\fR does the same, only it returns the shift count for the
last (most significant) bit set in the argument.
.SH RETURN VALUES
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 5n
No bits are set in mask.
.RE

.sp
.ne 2
.na
\fB\fIN\fR\fR
.ad
.RS 5n
Bit \fIN\fR is the least significant (\fBddi_ffs\fR) or most significant
(\fBddi_fls\fR) bit set in mask. Bits are numbered from \fB1\fR to \fB64\fR,
with bit \fB1\fR being the least significant bit position and bit \fB64\fR the
most significant position.
.RE

.SH CONTEXT
This function can be called from user, interrupt, or kernel context.
.SH SEE ALSO
\fIWriting Device Drivers\fR
